This article suggests that part of `jil(叱)` in Hyang-ga described a existent verb, `si-`, on the basis of the fact that `jil(叱)` can be read as `*si`. To verify the suggestion, the construction of `eumjilda(音叱多/□□ i)` in Hyang-ga and Gugyeol were systematically investigated. From this study, it could be seen that `eumjilda(音叱多)` in Hyang-ga and `eumjilda(□□ i)` in Seokdok Gugyeol realized the existent meaning as well as the obligatory meaning. In addition, for the `eumjilda(音叱多)` and `eumjilda(□□ i)`, the existent meaning was realized by `jil(叱/□)`, not `eum(音/□)`. This fact implies that the `jil(叱)` was grammaticalized from a existent verb, `si-`. Therefore, the `*si` is the phonetic value of `jil(叱)` in `eumjilda(音叱多/□□i)`. In addition, the reliable bases were investigated that the formation of `s` resulted from the drop of a vowel, `i`, from `*si` which was a phonetic value of `jil(叱)`. In this article, four bases are suggested. First, Jiseop Sino-Korean which represented the genitive was changed. Second, there were some words showing that `s` in some stem-final of the 15th century was originally formed from `*si`. Third, there was no words having [si] sound beyond the second syllable with the exception of honorific prefinal ending in the 15th century. Last, there was a phonetic basis that the `i` drop from `si` was highly possible. When `i` is combined with `s`, the vowel is voiceless and formant is weakened, due to the aspiration of `s`.